Precision Guidance of Extracorporeal Shock Waves

Abstract

Described herein are apparatus for performing lithotripsy. The apparatus comprise a CT scanner and a shock wave tube for generating shock wave pulses for fragmenting kidney stones. The CT scanner includes a guidance system which is utilized to guide and control the position of the shock wave tube relative to a patient. The shock tube moves along an track which may be coupled to the CT scanner or which may be movable relative to the scanner. The track may be circular or semi-circular. The shock tube is movable about three orthogonal axes, which movement is controlled by the guidance system. A method for performing the lithotripsy using the apparatus is also described herein.

1 . An apparatus for performing lithotripsy comprising:
 a shock wave tube for generating shock wave pulses for fragmenting at least one kidney stone;   a CT scanner comprising; and   a computer for guiding said shock tube;   wherein said computer determines the location of said at least one kidney stone to be treated and obtains a volume rendering to determine a relationship between said at least one kidney stone and at least one surrounding structure; and   wherein said computer further comprises determines a shock wave path including an entry site on a patient using said volume rendering and for controlling movement of said shock wave tube during said lithotripsy.   
     
     
         2 . The apparatus according to  claim 1 , further comprising a track along which said shock wave tube moves. 
     
     
         3 . The apparatus according to  claim 2 , wherein said track is mounted to said CT scanner. 
     
     
         4 . The apparatus according to  claim 2 , wherein said track is movable relative to said CT scanner. 
     
     
         5 . The apparatus according to  claim 4 , wherein said track moves along two linear tracks mounted to a floor. 
     
     
         6 . The apparatus according to  claim 2 , wherein said track is semi-circular. 
     
     
         7 . The apparatus according to  claim 2 , further comprising micro switches along said track for detecting the position of said shock wave tube in said track and for transmitting at least one signal to said computer. 
     
     
         8 . The apparatus according to  claim 1 , wherein said shock wave tube is movable about three orthogonal axes. 
     
     
         9 . The apparatus according to  claim 8 , wherein said shock wave tube is mounted within a cylindrical sleeve having a central axis and a device for moving said shock wave tube relative to said cylindrical sleeve along a first axis parallel to said central axis. 
     
     
         10 . The apparatus according to  claim 9 , wherein said device for moving said shock wave tube along said first axis comprises a gear arrangement and a first motor controlled by said computer. 
     
     
         11 . The apparatus according to  claim 9 , wherein said cylindrical sleeve is mounted inside two concentric rings and wherein said cylindrical sleeve is pivotable about a second axis perpendicular to said first axles and an inner one of said rings is pivotable about a third axis substantially perpendicular to said first axis and said second axis. 
     
     
         12 . The apparatus according to  claim 11 , wherein said cylindrical sleeve is joined to said inner one of said rings by two axles and a second motor controlled by said computer and joined to one of said two axles, said second motor causing said cylindrical sleeve and said shock wave tube to rotate about said second axis. 
     
     
         13 . The apparatus according to  claim 12 , further comprising said inner one of said rings being joined to an outer one of said rings by two inner ring axles and a third motor controlled by said computer and joined to one of said inner ring axles, said third motor causing said inner ring and hence said shock wave tube to rotate about said third axis. 
     
     
         14 . The apparatus according to  claim 1 , further comprising a removable plastic cap fitted over said shock wave tube. 
     
     
         15 . The apparatus according to  claim 1 , wherein said CT scanner is a helical CT scanner. 
     
     
         16 . The apparatus according to  claim 1 , wherein said CT scanner is a non-helical CT scanner. 
     
     
         17 . The apparatus according to  claim 1 , wherein said CT scanner comprises a scanner having multi-slice detectors. 
     
     
         18 . The apparatus according to  claim 1 , wherein said CT scanner comprises a scanner having sub-second scanning time. 
     
     
         19 . A method for performing lithotripsy comprising the steps of:
 providing a CT scanner having a table and a guidance system;   placing a patient on said table;   performing a volume acquisition and reconstructing at least one image obtained from said volume acquisition to determine a location of at least one kidney stone;   performing a volume rendering to determine a relationship between said at least one kidney stone and at least one surrounding tissue;   using said guidance system to determine a shock wave path including at least one entry site on said patient from said volume rendering;   using said guidance system to position a shock wave tube so as to generate at least one shock wave along said shock wave path; and   generating at least one shock wave using said shock tube so as to fragment said at least one kidney stone.   
     
     
         20 . The method according to  claim 19 , further comprising:
 advancing said table until said at least one kidney stone is located in a plane of section at the isocenter of said CT scanner; and   generating single section imaging to monitor fragmentation and position of said at least one kidney stone during subsequent lithotripsy.   
     
     
         21 . The method according to  claim 19 , wherein said shock wave tube positioning step comprises:
 providing a track on which said shock wave tube moves; and   using said guidance system to move said shock wave tube along said track to a position for generating said at least one shock wave.   
     
     
         22 . The method according to  claim 21 , wherein said shock wave tube positioning step further comprises using said guidance system to move said shock wave tube about at least one of three orthogonal axes. 
     
     
         23 . The method according to  claim 19 , wherein said shock wave tube positioning step further comprises:
 providing said shock wave tube with a plastic rod having a spherical tip located at a maximal focal point of said shock wave tube; and   defining a reference position by positioning said spherical tip at an isocenter of a gantry of said CT scanner.   
     
     
         24 . The method according to  claim 19 , further comprising displaying said shock wave path as a graphical overlay on the volume rendering. 
     
     
         25 . The method according to  claim 19 , wherein the step of generating at least one shock wave comprises generating at least one shock pulse during a breathhold having a duration of about 5 to about 10 seconds. 
     
     
         26 . An apparatus for performing lithotripsy comprising:
 a shock wave tube for generating shock wave pulses for fragmenting at least one kidney stone;   a removable plastic cap fitted over said shock wave tube;   a CT scanner comprising a computer for guiding said shock tube;   wherein said computer determines the location of said at least one kidney stone to be treated and obtains a volume rendering to determine a relationship between said at least one kidney stone and at least one surrounding structure; and   wherein said computer further determines a shock wave path including an entry site on a patient using said volume rendering and for controlling movement of said shock wave tube during said lithotripsy.   
     
     
         27 . The apparatus according to  claim 26 , further comprising a rod extending from said plastic cap along an axis of said shock wave tube. 
     
     
         28 . The apparatus according to  claim 27 , wherein said rod has no x-ray attenuation. 
     
     
         29 . The apparatus according to  claim 27 , wherein said rod comprises a sphere of radioopaque epoxy resin at its tip. 
     
     
         30 . The apparatus according to  claim 29 , wherein said sphere has a diameter less than about 1.0 mm. 
     
     
         31 . The apparatus according to  claim 29 , wherein said rod has a length such that said sphere is positioned at the maximal focal point of the shock wave tube.